Wall plug



Jan. 2, 1934. .1. J. RAWLINGS 1,942,256

- WALL PLUG Filed April 21, 1930 Patented Jan. 2, 1934 WALL PLUG John Joseph Rawlings, London, England, as-

signs! of one-half to The Rawlplug @ompany Limited, London, England Application April 21, 1930, Serial No. 446,043, and in Great Britain April 11, 1930 3 Claims.

This invention relates to improvements in wall plugs of the tubular type intended to be inserted in a hole made for that purpose in plaster, brickwork, stone or like material, in order to serve as a means for securing in the said hole a nail, screw or like holding device inserted in the bore of the p ug.

According to this invention, in the manufacture of a wall plug of plastic material including a proportion of a fibrous material, for example, a mixture of albumen and asbestos fibre, of a consistency such that it can be brought to a tubular formation by extrusion, after the plastic material has been brought to this tubular form and befor the plastic material has set or hardened, is given a torsional or helical twist.

As will be understood, when a mixture such as hereinabove mentioned is extruded through an annular space between a mandrel and a die, owing to the drawing action of the die there is a tendency for the individual fibres to take up a longitudinal position in the extruded tube. In some cases, in the use of the wall plug, the internal or bursting pressure applied to the tube by the insertion of a nail or screw, owing to this longitudinal arrangement of the fibres, may cause the plug to burst along a single longitudinal line and then there is a liability that the nail or screw may be deflected by the material of the plug or have a tendency to pass out through the split on one side of the tube, and thus assume an oblique position in the hole instead of being held with its axis coinciding with the axis of the said hole.

It has been found that, by giving to a wall plug a tendency to burst along a helical line or lines, the nail or screw is held centrally in the hole by parts of the plug, if burst, forming a wrapping about parts of the nail or screw. By this invention it is sought to give to a tubular plug of plastic material, as above mentioned, a tendency to burst along helical lines, by giving to the tubular extruded material as it leaves the forming die, and before the material of which it is composed has become set or hardened, a helical twist with a view to causing the individual fibres of the fibrous material comprised in the material oi the plug, to likewise assume a corresponding helical formation so that the wall plug under internal pressure applied thereto has a tendency 50 to burst or split along corresponding helical lines between the fibres.

The improved wall plug can be conveniently manufactured by means of apparatus constructed substantially as hereinafter described with referj ence to the accompanying drawing, wherein:

Figure 1 is a longitudinal sectional view of such apparatus, and

Figure 2 is a longitudinal sectional view of a wall plug embodying the invention.

As shown in this drawing a is a cylinder having a plunger 1) movable therein to effect the extrusion of plastic material from the cylinder through a nozzle c fitted with a tubular die 01, and an axial mandrel e, thus providing between them an annular space through which plastic material can be extruded by the plunger 2) from the cylinder at in a tubular form. A second tubular die I is rotatably mounted on the die d in alignment therewith, a flange g on the die ,7 being formed with a recess or shoulder to receive a flange h on the die it held therein by a segmental plate 2'. Means are provided whereby the die ,7 can be rotated, for example, a worm wheel 7' on the flange g in engagement with a worm is on a spindle Z which can be rotated in any convenient manner to impart rotary motion to the die j. The mandrel 6 can be conveniently extended into the die I.

Plastic material extruded through the annular space m between the die dand mandrel e, passes into the die which is formed with a bore of a suitable diameter so that some degree of friction is exerted by the interior wall of the die upon the moulded plastic material passing through it. When the said die f is set in rotation at an appropriate speed whilst moulded plastic material, fed thereto from the die at which is stationary, is passing through it, a suitable helical twist is given to the tubular extruded material Whilst it is in a sufiiciently plastic state. The tubular material extruded from the die 7 thus twisted can be subsequently set or hardened and cut into pieces of the required length for use as wall plugs, or it can be cut into suitable lengths on leaving the die and the plugs thus formed may be set or hardened separately. The rotary movement imparted to the plug in course of manufacture, before it leaves the stationary mandrel ensures the formation of the hole or bore through the plug concentrically to the outer surface of the same, that is to say the rotary movement of the extruded material tends to hold the mandrel e centrally in the die f.

There is thus provided, as shown in Figure 2, a wall plug 1 of extruded plastic material 2 including a proportion of a fibrous material 3 having an inherent tendency, when subjected to internal pressure, to burst along one or more helical lines so that on the plug bursting under the internal pressure applied by a nail or screw, parts of the the extruded material have a right hand twist and other parts a left hand twist.

I claim: 1. A wall plug, comprising a tubular cylindrical body of semi-plastic material and fibers irregularly embedded therein extending in a helical diplug still retain positions helically or circumferentially around the nail or screw, these parts serving to hold the nail or screw centrally in the plug and avoiding any condition liable to cause deflection of the nail or screw as it is driven in.

The rotation of the die 2 may be arranged to give a continuous right or left hand twist to the tubular extruded material or it can be rotated in opposite directions alternately so that parts of JOHN JOSEPH RAWLINGS. 

